An excellent, 27-part video tutorial series on using SuperCollider.

A number of free soundfonts for download.

First it was Cakewalk Pro Audio, then it was Sonar, and now it's Cakewalk by BandLab. Regardless of name, it's now a powerful (and free!) DAW.

Windows only, unfortunately. It also requires a BandLab account.

An Ardour template for symphonic composition. Includes Virtual Playing Orchestra, LinuxSampler integration, and more.

Symphony No. 2 in D Major, by Niilo Korsulainen, available on MuseScore.

1582 and 1625 additions to Piae Cantiones, available in PDF format.